Response bias affects perceptual asymmetry scores and performance measures on a dichotic listening task.

A dichotic listening paradigm discussed by Sidtis and Bryden (Neuropsychologia, 1978, 16, 627-632) allows one to present non-verbal as well as verbal material. This paradigm also permits signal-detection analyses to separate response biases from discrimination abilities. The present study used Sidtis' (Neuropsychologia, 1981, 19, 103-112) Complex Tone Task as an example of the paradigm. Employing signal-detection analyses, we demonstrated that commonly used performance and asymmetry indices are confounded by response bias. Several indices based on signal-detection measures are suggested to replace current widely used measures. As pointed out by Bryden and Sprott (Neuropsychologia, 1981, 19, 571-581), currently the usefulness of a perceptual asymmetry score is mainly determined by mathematical and statistical properties rather than by a theoretical framework. Thus, the choice of a particular index based on signal-detection theory is arbitrary. The present results and those of Katsuki et al. (Journal of Speech and Hearing Research, 1984, 27, 444-448) suggest that the confounding effect of response bias may be present in a variety of experiments investigating lateral processing.